Hydrorosin acid salts in the emulsion polymerization of styrenes



Patented May 13, 1952 HYDROROSIN sm SALTS IN THE EMUL- SION POLYMEBIZATION or STYRENES p v Joseph N. Borglin, Wilmington, DeL, and Philip A.'Ray', Denver, 0010., assign'ors to Hercules Powder Company, Wilmington',"Del., a corpo- Y ration of Delaware No Drawing. Original application June 17, 1944,

Serial No. 540,886. Divided and this application August 19, 1948, Serial No.;45,2 16

This invention relates to an improved process forthe emulsion polymerization of unsaturated compounds and, more particularly, to animproved process of polymerizing vinyl hydrocaricons to provide improved synthetic rubberlike materials. 1

It is well known that unsaturated compounds,

particularly those containing the vinyl group, may

beadvantageously polymerized in aqueous emulsion. Synthetic rubberlike materials have been Fatty acid soaps, although effective emulsifying agents for the polymerization of vinyl compounds, are not 'sufliciently water-soluble and are, therefore, quite difficult to remove from the polymerization products. The presence of fatty acids in the polymer has many disadvantages. Their presence in transparentplastic materials causes cloudiness. In the case of rubberlike polymers, the fatty acid soap remaining in the polymer is converted to free fatty acid, when salt and acid are needed, as is commonly done, in the precipitation of the polymer. Fatty acids weaken the rubber and must, therefore, be removed from it and their complete removal is very difficult.

Now in accordance with this invention, it has been found that the alkali metal salts of hydrorosin acids may be used, with very advantageous effects, as emulsifying agents for the polymerization of compounds which are capable of being polymerized by a peroxide-type catalyst and which contain the group CHFO where X is selected from the group consisting of alkyl, alkenyl, alkadienyl, alkynyl, alkoxy, aryl, aryloxy, halogen, acyl, acyloxy and cyano and Y is selected from the group consisting of hydrogen, alkyl and aryl.

The alkali metal salts of hydrorosin acids have been found to be excellent emulsifying agents in the preparation of polymers by emulsion polymerization. They. also have the advantage of being 1 9Claims. (Cl. 260-27) readilywashed out of the polymer and, as a result," transparent plastic polymers prepared by this means are free from cloudiness. Furthermore, the presence of hydrorosin acids has been found to materially increase the tensile strength and tack in rubbery polymers, such as the copolymer of butadiene and styrene. The physical properties after cure of these polymers are also improved.

"The following examples are illustrative of the preparation of polymers by emulsion polymerization and the products thereof in accordance with this invention. All parts given in the examples represent parts by weight.

. Emmple I Ten parts of dihydroabietic acid in 400 parts of water were neutralized with sodium hydroxide and 0.6 part of potassium persulfate, 1 part of lauryl mercaptan, 50 parts of styrene and 150 parts of butadiene were added. The mixture was agitated at 50 C. for 14 hours in a sealed container. The emulsion was then run into an open vessel containing 20 parts of a 2% aqueous solution of phenyl-fl-naphthylamine and stripped of excess butadiene. The polymer was precipitated by the addition of an'excess of a saturated salt solution, washed alkali-free with water, then washedwith alcohol and finally dried to constant weight on a mill. A 69% yield of polymer was obtained.

' Example II .This example was carried out exactly as described in Example I except that tetrahydroabietic acid was substituted for the dihydroabietic acid used in that example. A 78% yield of polymer was obtained.

Emmple III To 400 parts of a 2 /2% aqueous solution of sodium tetrahydroabietate containing an excess of 200% of sodium hydroxide solution, 6 parts of potassium persulfate, 45 parts of styrene, 136 parts of butadiene and 1.6 parts of isoamyl alcohol were added. The mixture was agitated at 50 C. for 16 hours in a sealed container. An 82% yield of polymer was obtained by precipitation with a concentrated salt solution.

In order to compare the use of a purified hydrorosin acid soap with that of ordinary rosin soap,

' the. following control was run: To 400 parts of parts of styrene and 136 parts of butadiene.

On carrying out the polymerization as described.

This example was carried out exactly as described in Example III using sodium tetrahydroabietate except that isoprene was substituted for the butadiene used in that example. A 69% yield of polymer was obtained.

Example V N wood rosin was distilled under a pressure of 2 mm. of mercury and the following fractions were collected: A light end of 12% was taken at a vapor temperature of about 250 C. and a second cut of 79% of the total charge was taken at a vapor temperature of about 300 C., leaving a residue of 8%.

The middle fraction of the distilled rosin was. hydrogenated in the molten state at 235 C. with a Raney nickel catalyst and hydrogen at a pressure of 5000 pounds per square inch for 3' hours, i. e., until no further hydrogen absorption was apparent. The hydrogenated rosin was then dissolved in gasoline, filtered to remove the catalyst, and the gasoline removed by distillation.

The hydrogenated rosin was? saturated to the extent of about 65% of both double bonds.

Ten parts of this distilled hydrogenated rosin in 400 parts of water were neutralized with sodium hydroxide and 5.5 parts of tertiary-butyl hydroperoxide solution (60% peroxide), parts of acrylonitrile, and 150 parts of butadiene were added. The mixture was agitated at 50C. for 14 hours in a sealed container- The. polymer was precipitated, washed, and dried as described in Example I. A 79% yield of butadiene-acrylonitrile polymer, was obtained.

Example VI Ten parts of tetrahydroabietic acid in 400' parts of water were neutralized with sodium hydroxide and 200 parts of styrene containing 0.2 part of benzoyl peroxide were added. The mixture was agitated in a nitrogen atmosphere at 50 C. for 16 hours in a sealed container. The polymer was precipitated, washed and then dried to constant weight in a vacuum oven at C. A yield of polymer was obtained.

The hydrorosin acid soaps described in ace cordance with this invention are prepared. by the saponification of hydrorosin acids with an alkali metal compound, basic. in nature. Alkali metal compounds suitable for this purpose are the hydroxides, carbonates, etc., of sodium, potassium, etc. The soap may be prepared in situ, i. e., the hydrorosin acid may be added tothe monomeric material and a solution of alkali added, or the soap may be incorporated in the polymeri-zation mass in the form of a paste, or in the form of a dry soap.

It will be understood that by purified hydrorosin acid is meant, in addition to the pure hydrorosin acids or mixtures thereof, a hydrogenated rosin, at least 50 per cent saturated with hydrogen, which has been purified by distillation, crystallization or other means to remove materials which inhibit polymerization with peroxide-type catalysts. It is well known that rosin is a mixture of isomeric rosin acids, the

best known of which are abietic acid, sapinic acid and d-pimaric acid. The relative proportions in which these and the other isomeric rosin acids occur in a given sample of rosin depend on the source of the rosin. Thus, wood rosin contains more abietic acid than any of the other acids, while American gum rosin contains more sapinic acid and French gum rosin contains more d-pimaric acid. Any of these rosins may be treated to reduce their unsaturation and the hydrorosin acids produced are equivalent for the purpose of this invention. The several isomeric acids found in various types of rosinv may be separated and hydrogenated in pure form or the hydrorosin acids may be separated after hydrogenation of the rosin, if desired.

The hydrogenation of rosin or rosin acids may be carried out by contacting the rosin or rosin acid in a fluid state with hydrogen in the presence. of an active base metal hydrogenation catalyst, such as. activated nickel, Raney nickel, copper-chromite, cobalt, etc., under pressure, for example 200 to 15,000 pounds per square inch, and at a temperature of about to about.

225 C. for about 0.5 to 5 hours. A highly active platinum or. platinum oxide catalyst may also be employed, in which case the reaction is usually carried out at room temperature under relatively low pressure and in the presence of an inert reaction medium such as acetic acid. Many other variations of the hydrogenation reaction may be utilized.

As pointed out above, either gum or wood rosin or the rosin acids may be hydrogenated. The rosin. may be refined prior to its hydrogenation, by anysuitable, method, as by distillation, heattreatment with or without a catalyst, solvent refined as with furfural, phenol, etc., or treated with an absorbent as fullers earth, activated carbon or refined by any other method. v

While fatty acid soaps are the most com monly used soaps for emulsion polymerization reactions,,they have many disadvantages as noted above. Ordinary; rosin soaps, on the other. hand, are not practical emulsifying agents for these reactions since they result in low yields of. polymer. However, by using the soaps of hydrorosin acids as emulsifying agents, the. yield of polymer is high at a satisfactory rate or comparable to that of the fatty acid soaps. These facts are, clearly illustrated by the foregoingiexamples. In addition to these advantages the polymer formed is consistently more uniform in its tensile properties than when fatty acid soaps are used as the emulsifying agent.

In contrast to fatty acids which weaken synthetic rubbers, hydrorosin acids have been found to: producev beneficial effects on these rubbers. The. tensile strength, elongation, tack and other physical properties are improved by the presence of a hydrorosin acid inthepolymeric material. An amount of hydrorosin acid up to about 10 per cent is particularly advantageous.

One means of incorporating small amounts of hydrorosin acids in a rubbery polymer is through the use of alkali metal salts of these acids as emulsifying agents in the preparation of the polymer as shown in the foregoing examples. By carrying out the polymerization in an aqeous emulsion in the presence of these soaps, the addition of acid and. salt in the precipitation of the polymer precipitates the free hydrorosin acid in the polymer. The polymer may then. be washed until froma'bout 0 to about 5 per: cent of hydro.-

rosin acid remains in the polymer. This has the advantage of eliminating the necessity for washing the polymer completely free of the emulsifying agent, as has to be done in the case of fatty acid soaps, and at the same time permits a means of simply and uniformly incorporating a small amount of hydrorosin acid in the polymerized material. In fact, an additional amount of hydrorosin acid may be added to the polymer to provide an amount of up to about per cent by weight of polymer, in order to take advantage of the improvements made by the presence of hydrorosin acids in the finished product.

The rubberlike polymers formed by emulsion polymerization of butadiene and styrene in the presence of hydrorosin acid soaps and containing, as a result thereof, an amount of a hydrorosin acid up to about 10 per cent, exhibit exceptionally high tensile strengths and elongations when compounded and vulcanized. The tack, building properties, and mill behavior in the unvulcanized state are also noticeably improved. The hydrorosin acid may, if desired, be washed completely out of the polymer, and the resulting polymer will still have an improved millability over that of a polymer prepared with a fatty acid soap.

The alkali metal salts of hydrorosin acids may be used alone or combined with fatty acid soaps as the emulsifying agent in polymerization by the emulsion technique. One of the advantages in using such a mixed emulsifying agent is that certain'of the less expensive fatty acid soaps, which are themselves unsatisfactory for emulsion polymerizations, may be used when used in combination with a soap of a hydrorosin acid.

Compounds which may be advantageously polymerized in aqueous emulsion by means of the soaps of hydrorosin acids include butadiene and its hydrocarbon derivatives such as isoprene, dimethyl butadiene and phenyl butadiene, or other compounds containing the vinyl group such as styrene, e-methyl styrene, a-OhlOlO styrene, a-cyano styrene, olefins, acylic terpenes, vinyl alkyl or aryl ethers, vinyl alkyl ketones, acrylic acid esters, methacrylic acid or esters, vinyl halides, vinyl esters, etc. The alkali metal salts of hydrorosin acids have been found to be excellent emulsifying agents, particularly in the preparation of the copolymers of butadiene and styrene or acrylonitrile, isoprene and styrene or acrylonitrile, and other rubberlike copolymers, as well as in th preparation of polymers such as polyvinyl chloride, polyvinyl acetate, polystyrene, polymethyl methacrylate, and the various other addition polymers which may be prepared by the emulsion technique.

The polymerizations in which hydrogenated rosin soaps are used may be subjected to the same variations in reaction conditions, for example, concentration of reactants, temperature, pressure, etc., as those in which a fatty acid soap is used. The temperature of the reaction may vary from about 20 to about 100 0., preferably from about 40 to about 60 C., and the concentration of the emulsifying agent may be varied from about 1 to about 5 per cent, usually about 2 to about 3 per cent is sufiicient. The polymerization, in general, is carried out with the aid of a catalyst, such as a peroxide-type catalyst, potassium persulfate, etc. Hydrorosin acid soaps may also be used in combination with any desired initiator or other polymerization or processing aid.

This application is a division of our application 6 for United States Letters Patent, Serial No. 540,886, filed June 17, 1944, now Patent Number 2,569,447.

. What we claim and desire to protect by Letters Patent is:

1. The process which comprises polymerizing a monomeric material consisting of a styrene polymerizable with a peroxide catalyst and containing the CH2=C group in aqueous emulsion in the presence of an alkali metal salt of a purified hydrorosin acid as the emulsifying agent.

2. The process which comprises polymerizing a monomeric material consisting of a styrene polymerizable with a peroxide catalyst and containing the CH2=C group in aqueous emulsion in the presence of an alkali metal salt of a distilled hydrorosin acid as the emulsifying agent.

3. The process which comprises polymerizing a monomeric material consisting of a styrene polymerizable with a peroxide catalyst and containing the CH2=C group in aqueous emulsion in the presence of an alkali metal salt of a crystallized hydrorosin acid as the emulsifying agent.

4. The process which comprises polymerizing a monomeric material consisting of a styrene polymerizable with a peroxide catalyst and containing the CH2=C group in aqueous emulsion in the presence of an alkali metal salt of a hydroabietic acid as the emulsifying agent.

5. The process which comprises polymerizing a monomeric material consisting of a styrene polymerizable with a peroxide catalyst and containing the CH2=C group in aqueous emulsion in the presence of sodium dihydroabietate as the emulsifying agent.

6. The process which comprises polymerizing l a monomeric material consisting of a styrene polymerizable with a peroxide catalyst and containing the CH2=C group in aqueous emulsion in the presence of sodium tetrahydroabietate as the emulsifying agent.

7. The process which comprises polymerizing a monomeric material consisting of styrene in aqueous emulsion in the presence of an alkali metal salt of a purified hydrorosin acid as the emulsifying agent.

8.. The process which comprises polymerizing a monomeric material consisting of styrene in aqueous emulsion in the presence of sodium tetrahydroabietate as the emulsifying agent.

9. The process which comprises polymerizing a monomeric material consisting of styrene in aqueous emulsion in the presence of sodium dihydroabietate as the emulsifying agent.

JOSEPH N. BORGLDT. PHILIP A. RAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,005,295 Meisenburg June 18, 1935 2,029,410 Carothers et al. Feb. 4, 1936 2,264,173 Collins Nov. 25, 1941 2,338,517 Kitani et al. Jan. 4, 1944 2,338,477 'Fryling Nov. 6, 1945 2,388,600 Collins Nov. 6, 1945 OTHER REFERENCES Mark et al.: High Polymeric Reactions, Interscience, 1941, pages 81 to 83 and 329. 

1. THE PROCESS WHICH COMPRISES POLYMERIZING A MONOMERIC MATERIAL CONSISTING OF A STYRENE POLYMERIZABLE WITH A PEROXIDE CATALYST AND CONTAINING THE CH2=C$ GROUP IN AQUEOUS EMULSION IN THE PRESENCE OF AN ALKALI METAL SALT OF A PURIFIED HYDROROSIN ACID AS THE EMULSIFYING AGENT. 